\begin{tikzpicture}[>=Stealth]
    \draw [->] (-3.5,0) -- (2.0,0) node[anchor=north] {$x$};
    \draw [->] (0,-1) -- (0,3.5) node[anchor=east] {$y$};
    \node at (-0.3,-0.3) {$O$};
    \draw (0,0) -- (130:3) node[anchor=south] {$\alpha$的终边};
    \draw [fill=black] (130:2) circle(1pt) +(0.5, 0.3) node {$P(x, y)$};
    \node at (-0.7,1.1) {$r$};
\end{tikzpicture}
